Effect Of Wind Barrier Structural Parameters On The Driving Wind Environment And Vortex-induced Vibration Of Twin-box Girder

After the addition of wind barriers,the wind environment above bridge deck and vortexinduced vibration of the twin-box girder are complex.It is of great significance to study the influence of wind barrier structure parameters on its driving wind environment and vortexinduced vibration performance.In order to explore the windproof mechanism of wind barriers and the aerodynamic mechanism affecting the vortex-induced vibration performance of twinbox girders,this paper designs five windproof ratio and four height ratios of wind barriers for wind tunnel test and numerical simulation.The main research contents include:(1)Through the numerical simulation of static flow around,the driving wind environment of the bridge deck of the twin-box girder with and without wind barriers is calculated.It is found that the shape of the wind profile of the bridge deck of upstream and downstream boxes of the main girder is inconsistent.With the increase of wind barrier windproof ratio and height ratio,the windproof height ratio and windproof area of the wind profile of the main girder bridge deck lane position gradually increase.The crosswind reduction coefficient of the upstream box at the calculated height of 2m does not increase but decreases,and the crosswind reduction coefficient of the downstream box gradually increases.The crosswind reduction coefficient at the calculated height of 4.5m shows an increasing trend.(2)Based on the wind tunnel test results,the influence of the structural parameters of the wind barrier on the vortex-induced vibration performance of the twin-box girder is compared and analyzed.It is found that the wind barrier can completely suppress the vertical bending vortex-induced vibration of the twin-box girder in the low wind speed area,which leads to the advance of the starting vibration reduction wind speed and the decrease of the length of the locking interval of the main girder in the high wind speed area.The dimensionless maximum vertical amplitude of the high wind speed area of the twin-box girder increases with the increase of the wind barrier windproof ratio,and increases first and then decreases with the increase of the wind barrier height ratio,reaching the maximum when the height ratio is 0.6.The vibration reduction wind speed increases with the increase of the wind barrier windproof ratio and the height ratio,and the change rule of the lock-in interval length is not significant.(3)Based on the characteristic conditions of the vibration test,the numerical simulation of the vibration state is carried out to study the influence of the structural parameters of the wind barrier on the flow field characteristics of the twin-box girder.The results show that the wind barrier can reduce the vortex scale around the cross section in the low wind speed area,weaken the flow separation and airflow acceleration of the incoming flow,form a stable and narrow vortex,and greatly reduce or even disappear the vortex in the wake area,thus suppressing the vertical bending vortex-induced vibration in the low wind speed area of the main girder.With the increase of the windproof ratio of the wind barrier,a large-scale vortex is formed on the leeward side of the wind barrier,and the scale and influence range of the vortex around the flow field are increasing.With the increase of the height ratio of the wind barrier,the vortex scale and the influence range of the vortex increase first and then decrease,and the maximum value appears at the height ratio of 0.6.